Hello, λanim!

In this tutorial, we’re going to recreate the lanim.examples.hello animation.

1. Create a stub

Create a file called tutorial_hello.py with this content:

from lanim.examples.hello import export

Then run python -m lanim -o hello.mp4 tutorial_hello in the same directory.

This explains how to make lanim animate your module: it needs to export the animation under the export name.

2. Create the greeting

from lanim.pil import Latex

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

Theis object doesn’t do anything yet — it’s a simple value, like a number or a string.

3. Make a static animation of the greeting

from lanim.core import const_a
from lanim.pil import Latex

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

export = const_a(sign)

Now try python -m lanim -o hello.mp4 tutorial_hello and see what happens.

This animation is only 1 second long, how do we make it longer?

3. Stretch the animation

from lanim.core import const_a
from lanim.pil import Latex

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

export = const_a(sign) * 5

Render the video again. It should be five seconds long.

4. Make the sign scale out instead of just sitting there

from lanim.pil import Latex, appear

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

export = appear(sign) * 2

5. Create a border around the greeting

from lanim.pil import Latex, Rect

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

How do we animate both of them?

6. Animate a pair of the greeting and the border

from lanim.pil import appear, Latex, Rect, Pair

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

pair = Pair(sign, border)

export = appear(pair)

Pair is also an ordinary immutable value, like Latex and Rect.

7. Make the last frame persist for a while

You can put one animation after another by adding them:

from lanim.core import const_a
from lanim.pil import appear, Latex, Rect, Pair

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

pair = Pair(sign, border)

export = appear(pair) + const_a(pair)

8. Make the border appear before the sign

8.1. Make the sign appear inside the border

from lanim.core import const_a
from lanim.pil import appear, gbackground, Latex, Rect, Pair

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

pair = Pair(sign, border)

export = gbackground(appear(sign), [border]) + const_a(pair)

gbackground accepts an animation and a list of graphics to put in the background.

8.2. Stretch out the border before the greeting animation

from lanim.core import const_a
from lanim.pil import appear, gbackground, Latex, Rect, Pair

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

pair = Pair(sign, border)

export = appear(border) + gbackground(appear(sign), [border]) + const_a(pair)

8.3. Formatting tweak

from lanim.core import const_a
from lanim.pil import appear, gbackground, Latex, Rect, Pair

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

pair = Pair(sign, border)

export = (
    appear(border)
    + gbackground(appear(sign), [border])
    + const_a(pair)
)

9. Move the assembly down

from lanim.core import const_a
from lanim.pil import appear, gbackground, move_by, Latex, Rect, Pair

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

pair = Pair(sign, border)

export = (
    appear(border)
    + gbackground(appear(sign), [border])
    + const_a(pair)
    + move_by(pair, dx=0, dy=10)
)

---

The animation is doing the action we wanted it to do, but it’s not pretty. Let’s fix that.

10. Add easings

An easing function allows you to change the “shape” or “texture” of the change.

Animation

To illustrate, look at these easings:

• The linear easing moves at a steady pace. It doesn’t change an animation.
• The in-out easing has a gentle start and end
• The sled easing starts out slow and then accelerates

Formulas

An easing is a function from [0; 1] to [0; 1].

You can see their graphs in on Desmos

from lanim.core import const_a
from lanim.pil import appear, gbackground, move_by, Latex, Rect, Pair
from lanim.easings import in_out, sled

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

pair = Pair(sign, border)

export = (
    appear(border)
    + gbackground(appear(sign), [border]).ease(in_out)
    + const_a(pair)
    + move_by(pair, dx=0, dy=10).ease(sled)
)

11. Adjust durations

Timing is to animation what intonation is to speech.

Let’s spice our animation up by tweaking some of the durations.

from lanim.core import const_a
from lanim.pil import appear, gbackground, move_by, Latex, Rect, Pair
from lanim.easings import in_out, sled

sign = Latex(x=0, y=0, source=r"Hello, $\lambda$anim!")

border = Rect(
    x=0,
    y=0,
    width=sign.width() + 1,
    height=sign.height() + 1
)

pair = Pair(sign, border)

export = (
    appear(border) * 0.5
    + gbackground(appear(sign), [border]).ease(in_out)
    + const_a(pair) * 0.25
    + move_by(pair, dx=0, dy=10).ease(sled)
)

Recap

In this tutorial, you’ve learned how to:

1. Export a simple animation from a Python module
2. Create graphical objects, namely Latex, Rect and Pair
3. Animate still frames, as well as scale out and move objects
4. Change the duration of animations
5. Put animations in sequence
6. Use easings to make transitions more interesting